【作者】 邬华芝；

【导师】 高德平；

【作者基本信息】 南京航空航天大学 ， 航空宇航推进理论与工程， 2003， 博士

【摘要】 随着航空科技的飞速发展，要求提供推重比越来越高的航空动力。上世纪以来，整体焊接叶盘已在新研制的航空发动机上应用。目前，航空发动机整体焊接叶盘应用中尚存在的问题之一是焊接结构疲劳寿命的预测问题。本课题以航空发动机压气机叶盘常用材料钛合金(TC11)电子束焊构件为研究对象，对焊接接头的疲劳破坏行为，基于损伤力学理论分析其疲劳损伤演化规律，应用现代数学的新概念——分形几何学理论，建立宏观参量与细观损伤特征相联系的疲劳损伤模型，研究疲劳断口分维数测量方法以及分形损伤变量与疲劳寿命之间的关系，建立焊接接头疲劳损伤分形演化方程。对焊接结构疲劳寿命的预测有重要理论意义和实际应用价值。其创新点主要有： 1．采用分形维数定义了结构疲劳分形损伤变量，根据疲劳裂纹的分形扩展特点，建立了宏细观统一的结构疲劳损伤分形演化模型。该模型既反映了损伤细观结构的特性，又便于宏观参量的分析和研究 2．根据疲劳试验结果，获得了TC11钛合金焊接接头的疲劳特性，即最大加载应变与疲劳寿命的关系曲线。根据疲劳断口分维数的测量结果，获得了TC11钛合金焊接接头断口分维数与其疲劳寿命的关系曲线，以及断口分维数与最大加载应变之间的关系曲线，给出了进一步疲劳寿命预测的方法。 3．根据结构疲劳损伤分形演化模型，通过对TC11钛合金焊接试件的疲劳试验和疲劳断口分维数测量，得到了宏观损伤变量和分形损伤变量与疲劳寿命的关系，建立了TC11钛合金焊接接头的疲劳损伤演化方程。给出了进一步疲劳损伤量预测的方法。 4．金属疲劳断口分维数测量方法的研究是目前材料性能分析研究中的前沿课题。研究表明：放大倍数和测量码尺的选择因材料结构而异，对测量结果影响很大。本文应用数据处理技术研究了疲劳断口分维数测量中电镜放大倍数及测量码尺的选择问题，改进了二次电子线扫描分维数处理方法，并成功地应用于钛合金焊接接头断口分维数的测量，得到了有价值的分维数测量参数的选择范围，对进一步的研究具有重要意义。 本文研究表明：采用分维数定义损伤变量，建立结构的宏细观疲劳损伤演化模型，尤其是对于TC11钛合金这样的高强度材料结构，损伤量变化不易宏观测量，可以通过断口分维数与结构寿命关系的研究，有效地反映疲劳损伤过程。因此，它是一种研究焊接结构疲劳损伤过程的新途径。本文的研究结果，对航空发动机整体焊接叶盘疲劳寿命的预测具有重要意义和应用参考价值。更多还原

【Abstract】 With the rapid development of aero science, it requires the aero engine ratio of traction to weight is higher and higher. Since last century, whole welded blisc has been applied in aero engine new developed. Nowadays, it is still one of the problems of welded structure life forecasting in aero engine whole welded blisc application. Taking Ti alloy TC11 electron beam welded work-piece as research object, which is the conventional material of aero engine compressor blisc, the fatigue damage evolution law of fatigue damage action in the area of welded joint based on damage mechanics theory is analysed, and fatigue damage model, which macro-parameter and micro-damage characteristics are related, with fractal geometry-a new conception of modern mathematics is set up in this paper. It tries to research the measuring method of fatigue fracture fractal dimension and the relationship of fractal damage variable with fatigue life. It also sets up the welded joint fatigue damage fractal evolution equation. For weld structure fatigue life forecasting, it has important theory meanings and practical applying value. The innovations are following aspects:1. According to fractal propagation characteristics of fatigue crack, it defines structure fatigue fractal damage variables and sets up the structure fatigue damage fractal evolution mode which macro and micro are consistent. The mode not only reflects damage microstructure traits, but also makes it easy to analyze and research macro parameters.2. According to the result of fatigue experiment, it gets fatigue traits of Ti alloy TC11, which is the relationship curve of the maximum loading strain range with fatigue life. According to the measuring result of fatigue fracture fractal dimension, it gets the relationship curve of Ti alloy TC11 welded joint fracture fractal dimension with loading strain range, and the method of fatigue life forecasting fatherly.3. According to the model of structure fatigue damage fractal evolution, the relation between macro-damage variable, fractal damage variable and fatigue life can be found, and the fatigue damage evolution equation of Ti alloy TC11 welded joint can be built, and the method of more forecast fatigue damage is given.4. The research of metal fatigue fractal dimension measuring is in the study of materialcharacteristic analyzing. It demonstrates: the selection of magnifying multiple and measuring size are different to material structure, and the measured result is greatly influenced. The selections of electron microscope magnifying multiple and measuring size in fatigue fracture fractal measure are studied in this paper, and the improved treatment of secondary electron lines scanning fractal dimension, is applied successfully to the measuring of Ti alloy welded joint fracture fractal dimension and the valuable selective range of fractal dimension measuring parameter is got, which is very important to further research.Using fractal dimension defining damage variable and building macro and micro-fatigue damage evolution model of structure are suggested in this paper. The variety of damage which is not easy macro-measured to Ti alloy TC11 whose material structure is high intensity can reflect fatigue damage process effectively by studying the relation between fracture and structure life. So, it is the new method of researching welded structure fatigue damage process. The obtained result is very important to the life forecasting of welded blisc of aero engine, and has appliance reference to the future.更多还原